The site admin does not write creepypasta (though that’s not to say I’ve banned myself from contributing, but I’m usually far too busy reading submissions to consider writing anything myself nowadays), I just read all the submissions and decide which ones to accept and publish.
The second point is just part and parcel of the blogging software that this site uses. Since you’ve only got one person scheduling posts here, it follows that every single post will be by that user account. It makes more sense if you read it as ‘This entry was posted by (admin name here).’ It’s not actually any attempt at taking credit for the story, don’t take it as such. If you scroll to the bottom of any given pasta, you’ll see that if the user requested named credit, it will be given there.